If you have lived in Australia for 12 months in the past 10 years then you could qualify for and you would be required to have an AFP police check for which there are websites online that could assist you with the process. You will have to apply through the right website as there are several that you could refer to provided that you actually qualify to have an Australian Federal police check.
Apart from being required to have spent at least one year in the last 10 years in Australia, you would also be expected to be over and above the age of 16. If you qualify then you should be referring to an authorised website so they could process your application or mediate the application process for you.
You will be charged fees for the process but if you are doing volunteering work and you belong to a certain category of employees then you may not be required to pay for it. However, you will have to follow an alternative route to get your afp police check.
It would to be ideal if you can proceed directly through the Australian Federal police website or even pay them a visit and see what they could recommend for people in your category of employment. If however, you are simply considering to take up employment in a professional capacity and your employer has asked for a police check then you would definitely have to pay the fee.